If your question is about finding one key out of several, the only way I've done that is by building another hash with the value pointing toward the key. If you're doing this, you should consider making it a hash of lists, because while you can only have one value for each key, you can have multiple keys pointing to identical values, and turning a normal hash inside out like this can cause you to drop data if you don't store it in a list.

If I can, I try to build both hashes simultainously.

If I'm totally off my rocker, and this isn't a good way to handle the situation where you need to find one key out of several, I'd love to know more about it.

Update:I'm a total loser. I re-read the original post and I just realised that this question wasn't about finding one key out of several... D'OH!